Print processing of the diffusion transfer type involves submerging a paper negative and a receiver sheet into a solution out of contact with one another, and then withdrawing them from the solution in contact or laminated with one another. The sheets are pressed together to remove the solution and to provide the intimate contact of the two sheets which is required for chemical transfer of the image to occur. The product of the correctly accomplished process is an image of very high quality, for example of the type frequently called a "stat", which is a very detailed and fine line high contrast quality image.
Such a process has a number of important inherent requirements, and if any of them is not fulfilled, then a superior product will not be made. For example, the emulsion sides of the sheets must not make contact with one another or any other surface while they are wet with solution, except at the precise moment when transfer is to be made. This contact must be accomplished without "shear" or slip-type motion between them. They can be allowed to make contact with one another while dry before immersion, but permissible contact after immersion is limited to the precise moment of transfer. The pressure applied to press the sheets together and to remove the solution from them must be uniform across the product. The sheets must be protected against being scratched during insertion, processing and removal, and residues especially silver residues, that remain in the system from previous processing must not be entrained.
It should be remembered that this process takes only a relatively short period of time, which time should be kept to a minimum, and is done in a dark room with red safe light. A suitable processor must be simple in construction and easy to use, or spoilage of expensive material is likely to occur. Furthermore, the processor itself should, if possible, be inexpensive to manufacture so that it can be sold at a reasonable price. Also, recovery of silver should be reasonably easy, because it is a high value residue.
In addition, the solution itself presents some difficulties. It is subject to oxidation and evaporation by the air, and the rate of oxidation is rougly proportional to the amount of exposed area of solution. When a horizontal tank is used, there is a large exposed area, which it is difficult to close off from the air to prevent the entry of new oxygen to replace that which has already reacted with the solution. Thus, the rate of oxidation of this costly solution is frequently quite high in conventional processors, and the solution must frequently be replaced.
This invention provides a processor with no part which must be moved during processing, for example, motors or driven rollers, and which overcomes all of the above disadvantages. The processor is inexpensive to manufacture, reliable and easy to use, and because of its vertical orientation presents only a minimal area to air where oxidation occurs. It can be closed to exclude new air, and thereby further reduces chemical costs.